Cal. Civ. Proc. Code § 2020.220

(a) Subject to subdivision (c) of Section 2020.410, service of a deposition subpoena shall be effected a sufficient time in advance of the deposition to provide the deponent a reasonable opportunity to locate and produce any designated business records, documents, electronically stored information, and tangible things, as described in Article 4 (commencing with Section 2020.410), and, where personal attendance is commanded, a reasonable time to travel to the place of deposition.
(b) Any person may serve the subpoena by personal delivery of a copy of it as follows:
1. (1) If the deponent is a natural person, to that person.
2. (2) If the deponent is an organization, to any officer, director, custodian of records, or to any agent or employee authorized by the organization to accept service of a subpoena.
(c) Personal service of any deposition subpoena is effective to require all of the following of any deponent who is a resident of California at the time of service:
1. (1) Personal attendance and testimony, if the subpoena so specifies.
2. (2) Any specified production, inspection, testing, and sampling.
3. (3) The deponent’s attendance at a court session to consider any issue arising out of the deponent’s refusal to be sworn, or to answer any question, or to produce specified items, or to permit inspection or photocopying, if the subpoena so specifies, or specified testing and sampling of the items produced.
(d) Unless the subpoenaing party and the subpoenaed person otherwise agree or the court otherwise orders, the following shall apply:
1. (1) If a subpoena requiring production of electronically stored information does not specify a form or forms for producing a type of electronically stored information, the person subpoenaed shall produce the information in the form or forms in which it is ordinarily maintained or in a form that is reasonably usable.
2. (2) A subpoenaed person need not produce the same electronically stored information in more than one form.
(e) The subpoenaed person opposing the production, inspection, copying, testing, or sampling of electronically stored information on the basis that the information is from a source that is not reasonably accessible because of undue burden or expense shall bear the burden of demonstrating that the information is from a source that is not reasonably accessible because of undue burden or expense.
(f) If the person from whom discovery of electronically stored information is subpoenaed establishes that the information is from a source that is not reasonably accessible because of undue burden or expense, the court may nonetheless order discovery if the subpoenaing party shows good cause, subject to any limitations imposed under subdivision (i).
(g) If the court finds good cause for the production of electronically stored information from a source that is not reasonably accessible, the court may set conditions for the discovery of the electronically stored information, including allocation of the expense of discovery.
(h) If necessary, the subpoenaed person, at the reasonable expense of the subpoenaing party, shall, through detection devices, translate any data compilations included in the subpoena into a reasonably usable form.
(i) The court shall limit the frequency or extent of discovery of electronically stored information, even from a source that is reasonably accessible, if the court determines that any of the following conditions exists:
1. (1) It is possible to obtain the information from some other source that is more convenient, less burdensome, or less expensive.
2. (2) The discovery sought is unreasonably cumulative or duplicative.
3. (3) The party seeking discovery has had ample opportunity by discovery in the action to obtain the information sought.
4. (4) The likely burden or expense of the proposed discovery outweighs the likely benefit, taking into account the amount in controversy, the resources of the parties, the importance of the issues in the litigation, and the importance of the requested discovery in resolving the issues.
(j) If a subpoenaed person notifies the subpoenaing party that electronically stored information produced pursuant to a subpoena is subject to a claim of privilege or of protection as attorney work product, as described in Section 2031.285, the provisions of Section 2031.285 shall apply.
(k) A party serving a subpoena requiring the production of electronically stored information shall take reasonable steps to avoid imposing undue burden or expense on a person subject to the subpoena.
(l) An order of the court requiring compliance with a subpoena issued under this section shall protect a person who is neither a party nor a party’s officer from undue burden or expense resulting from compliance.
(m)
1. (1) Absent exceptional circumstances, the court shall not impose sanctions on a subpoenaed person or any attorney of a subpoenaed person for failure to provide electronically stored information that has been lost, damaged, altered, or overwritten as the result of the routine, good faith operation of an electronic information system.
2. (2) The subdivision shall not be construed to alter any obligation to preserve discoverable information.